1. Field of the Invention
This invention pertains to apparatus and methods for moving pipe back and forth between storage racks and a drilling rig floor. More particularly, it pertains to overall pipe moving systems as well as component features of the overall system.
2. Description of the Prior Art
The use of a skate for supporting the end of a pipe or the use of pairs of independent skates for simultaneously supporting the opposite ends of pipe as the pipe is moved to and from the drilling rig floor are known. One typical example is shown in U.S. Pat. No. 3,268,095. These systems, however, which have used single or plural skates are complicated in operation.
Various types of pipe delivery systems and tripping techniques for moving the pipe off a skate are also known. In some instances, the entire skate is tipped and in other instances, pipe ejector ramps are raised from below the skates to hit the pipe off the skate. An example of the latter is shown in U.S. Pat. No. 3,315,822. In this patent the skate consists of a pair of carriages arranged to carry the pipe along a horizontal track to a point where the derrick end of the pipe is elevated from its carriage by an air cylinder to move the pipe into an upwardly sloped position.
Several pipe handling systems have been tried for moving drill pipe from a ground level storage area to the elevated floor of an oil drilling rig for vertical coupling to the drill string. Since several hundred lengths of pipe are normally required to drill a hole and these must be tripped to replace the bit from time to time, speeding of the in-and-out process with a minimum of manual effort is important.
Various types of pipe transferring devices are known for moving pipe to and from vertically-spaced layers or racks of pipe. In some instances, the entire storage rack is hoisted to the desired skate level.